resolves #683 number sections in appendix using appendix number

- don't use normal numbering on appendix titles
- number subsections using appendix letter in first position
- use regular section numbering format when appendix-caption is blank
resolves #664 honor list continuations on indented, nested list items
Merge pull request #703 from mojavelinux/issue-664

resolves #664 honor list continuations on indented, nested list items
Merge pull request #691 from mojavelinux/issue-683

resolves #683 number sections in appendix using appendix number
resolves #300 copy custom stylesheet if linkcss is set